<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
       .father{
           width: 200px;
           height: 200px;
           display: flex;
           border: 1px solid red;
           justify-content: center;
           align-items: center;
       
        }
       .son{
           width: 50px;
           height: 50px;
          
           border: 1px solid black;
       }
    </style>
</head>
<body>
    <div class="father">
        <div class="son"></div>
    </div>
</body>
</html>